The purpose of the project is to study the organization of genes in large DNA molecules obtained from animal viruses. The production and ordering of unique segments of vaccinia virus DNA provide a physical map of the genome. Physical maps have been determined for several different restriction enzymes. I am also working to improve the techniques for separating and isolating very large pieces of DNA which differ in size and base composition by relatively small amounts. In particular, I am trying to isolate the DNA segments which contain the origin(s) of replication of vaccinia DNA and to test for possible signal elements in the DNA without prior knowledge of the nucleotide sequence.